1. Field of the Invention
The present invention relates to wall fixtures for piping and the like. More particularly, the present invention relates to non-leak wall fixtures for installation in an aquatic environment such as pools, spas and the like. Even more particularly, the present invention relates to improved fitting designs which resist leaking and methods for installing the improved fitting designs. Still more particularly, the present invention relates to wall fittings and the like that rely on plaster for making a hydraulic seal and are typically installed with their bodies in a horizontal orientation and installation method for the fittings.
2. Description of Related Art
The construction of an in-ground pool (or spa) may be accomplished through the use of various construction platforms of which fiberglass, vinyl-liner pools and cement, are the most commonly used in inground pools. Fiberglass, or Kevlar (a registered trademark of the E. I. Du Pont De Nemours and Company Corporation, Wilmington, Del.), construction platforms make use of pool shells that are prefabricated off-site, with painted or epoxy-coated interior and then assembled on-site. Ports are provided in the fiberglass shell for the installation of water and light wall fittings. Typically, a hole is excavated in the ground, and then pipes are plumbed into positions corresponding to the ports. The vast majority of pool pipe and plumbing is manufactured from PVC (PolyVinyl Chloride) or ABS (Acrylonitrile Butadiene Styrene) plastics which are easily glued together to form rigid, watertight connections and able to withstand several hundred psi (pounds per square inch) internally, with even greater crush strengths. The fiberglass shell is disposed within the excavated volume and the plumbed piping is rigidly attached to the fiberglass body, thereby forming a positive hydraulic seal between the interior of the shell and the ground. Additional protection against leakage may be provided by installing gaskets or o-rings between the fiberglass shell and the pool fitting. The fiberglass shell may be installed from one or more separate component pieces which are fitted together with sealing gaskets in the excavation and then coupled to the pool plumbing. Level is maintained on the shell and dirt is backfilled around the fiberglass pool walls and plumbing. The fiberglass shell provides the structural support necessary for holding the pool water. Leakage around pool fittings in a fiberglass pool is uncommon, but any leaks which might develop are easily remedied by installing new o-rings or gaskets.
Vinyl liner pools are typically constructed from prefabricated wall panels that are fastened together and sit on a concrete foundation (or Vermiculite, mixtures of vermiculite and sand, Portland cement, and clay) in an excavated hole. The wall panels and foundation form the pool shell and provide the structural support for the pool liner, which contains the pool water. Prior to installation of the panels, the excavate volume is plumbed corresponding to ports provided in the panels for wall fitting placements. Dirt is backfilled around the wall panels and piping for lateral support. A liner, manufactured with exacting tolerances to fit the panel and foundation pool support configuration, is then disposed within the panels and on the foundation. Finally, holes are pierced in the vinyl liner corresponding to the position of plumbed ports (or the liner may have had the fitting holes precut) and the liner is coupled to the pool fittings and the wall panels and/or foundation. Because the fittings are designed to form a seal around both the wall panels and vinyl liner, leakage is fairly rare around the wall fitting. Gaskets or o-rings may also be installed to assure a hydraulic seal. Vinyl liner construction is generally not suitable for spas. Similar to the fiberglass pool platform construction, leakage around pool fittings in a vinyl liner is relatively uncommon, but any leaks which might develop are easily remedied by installing new o-rings or gaskets. Typically, when a leak develops in a vinyl liner, the leak must be repaired and the water trapped under the backside of the liner must be evacuated.
Probably the most popular type of in-ground pool construction platform is the cement shell type due primarily to its durability and infinite design configurability. Unlike fiberglass or vinyl liner pools, virtually the entire cement pool is fabricated on-site. The shape, size and placement of a cement pool does not depend on the prefabricated shape of a shell, wall panels or liner, and therefore it may be customized to fit a plethora of design and location choices. Another advantage to a cement pool construction platform is that the pool's dimensions may be designed to accommodate any shape or size yard, while complementing the existing landscape. Cement pools are also extremely adaptable to the owners' specific needs from fitness swimming to playing games.
Cement pool platforms require a much different construction approach than either fiberglass or vinyl liner pools because the waterproof pool shell is constructed on-site rather than being installed as a prefabricated unit. Additionally, a cement pool is typically more costly for the pool owner than the other pool types. Construction begins by excavating a volume of earth in accordance with the pool design. A steel cage of reinforcement bars (rebar) is assembled in the excavated volume. The tradesmen bend and tie steel rebar to form a grid-like pattern which is used to strengthen the pool's cement shell and provide rigidity. A wooden pool frame is typically constructed in conjunction with the pool cage and extends from the cage for delineating the upper wall edges, skimmer and spa transitions, steps, haul-outs and other above grade structures such as spas and spa walls, springs, waterfalls, etc. Input and return pipes are then plumbed and tied to the rebar cage as necessary. Each pipe end is designed to penetrate from the shell exterior to the pool's interior and terminate at an exact position on the shell. Certain fittings may require additional structural support from the main steel cage, such as skimmers, which are caged separately and then attached to the existing steel rebar cage of the pool shell. Pool fittings that are to be cemented in place are glued (or fitted) to the appropriate pipe ends, such as main drains (pool and spa), skimmer, light niches and the like. Other fittings, which are not intended to be cemented in place, are not installed. At this point, the plumbing is typically given an initial leak test (usually holding 20-50 psi for 8 to 24 hours depending on the construction code of the municipality), so all open pipes at the pump and pool ends are temporarily capped.
After passing the pressure test, the pool is ready for cementing. The cement products used in pool construction bare little resemblance to the conventional types of cement used in concrete construction. Typically, either “gunite” (Gunite or gunnite) or “shotcrete” is applied to the steel rebar cage and framing for creating a pool shell. Gunite is a trade name for concrete that is blown into place while shotcrete is the generic term used by the American Shotcrete Association. Both compounds are similar mixtures of water, Portland cement, calcium chloride (up to 20% for rapid mixing and curing), mason's sand and often very small pebbles and extra fly ash. The primary difference between gunite and shotcrete is the application of the cementation mixture; gunite is a “dry gunned” process while shotcrete is “wet gunned.” Dry gun means the dry ingredients of cement and sand are injected into an air stream in the proper proportions, conveying them to the nozzle. The operator (nozzleman) controls the water-cement ratio by varying the amount of water added to the nozzle with a special water-ring. The integrity of the mixture depends entirely on the accuracy of the onsite workers who adjust the mixing volumes of the dry ingredients and the experience of the nozzleman. Inconsistencies in the mixture of dry ingredients' amounts, and the water-cement ratio result in decreased and erratic compressive strength ratings of cured product, sometimes less than 2,000 psi. Coring tests conducted on various parts of pool walls have confirmed that the compressive strength may vary by as much as 4,000 psi from one core to the next. Furthermore, the amount of rebound, or the waste created by sprayed concrete falling to the floor, is very high due to erratic and improper water-cement ratios. Inconsistencies in the dry mix ingredients and the water-cement ratio also contributes to poor bonding between the cured cement and the pool fixtures.
Shotcrete is the solution to the shortcomings of the dry gun gunite approach. Most of the inconsistencies of dry gunning are overcome by using a computer controlled mix design from a concrete batch plant. The shotcrete is manufactured using regulated and exacting standards and transported to the job site as a wet material (emulsion) which is then pumped through a hose to a nozzle with an air-ring, allowing it to adhere to vertical walls with less rebound. Because the dry ingredients are mixed together with the water at the cement plant using a computer controlled process, the slurry transported to the job site is a homogenous mixture yielding a consistent compressive strength of between 3,000 psi and 4,000 psi. While bonding between the cured cement and the pool fixtures does not suffer due to “dry spattering,” as in the dry gun approach, bonding between the wet cement slurry and the pool fixtures is equally poor because during the initial curing stage water migrates from the mixture to the surface areas, thus forming a wet annulus between the pool fixtures and the curing cement.
Although the wet gun shotcrete approach seems far superior to the dry gun approach, pool contractors have been slow to embrace shotcrete due to its added cost over gunnite. Since shotcrete is a standardized mixture which is often regulated in its manufacture by state transportation and building agencies (notably California) due to its adoption for road and overpass construction, it is much more expensive for pool contractors. Independent tradesman often cannot justify the added expense of shotcrete over buying the dry ingredients for gunite separately and dry gunning the mixture.
In either case, during the pneumatic application of the cement, the entire rebar cage is covered, as is much of the exposed plumbing and fittings. Often the skimmer body and the steel cage surrounding it will be cemented in place with the pool shell. Spaces surrounding the temporarily capped pipe ends will then be troweled to form a space sufficient for receiving the fitting, most notably surrounding the side wall pipe ends in which conic-shaped indentation in the cement are troweled out for accepting the sidewall fitting. In so doing, the entire body of the fitting, up to the front opening, will reside behind the cement and plastered pool wall. Many cement manufacturers recommend to water cure the cement for 72 hours after hydration to slow and even out the drying times throughout the cement shell. Avoiding the uneven drying times increase the compressive strengths and reduces the likelihood of curing cracks.
Coping and ceramic is then installed on the cement pool wall. The skimmer throat flange is sealed now using a durable tile adhesive (a mastics adhesive or thin-set mortar), tile and grout. The remaining pool fittings (typically just the sidewall fittings) are installed by trimming the exposed pipe to the necessary length and gluing the sidewall fitting. Following the application of the pool tile, the exposed portion of the cement shell is plastered with a quarter inch deep layer of pre-blended pool plaster, often containing white marble (ground into small chips) for added luster. Also called whitecoat or marcite, pool plaster is an age old process of finishing many structures. Used underwater, it provides the watertight seal that the more porous gunite or shotcrete beneath it cannot. Other exposed color aggregates are available such as 3M Colorquartz™ (available from the 3M company of St. Paul, Minn.), PEBBLE TEC®, Durozzo and Hydrazzo which are each pool finish which incorporates larger aggregate (pebbles) than the marble chips in marcite, the pebbles are typically selected by their color.
While cement constructed pools are extremely popular with owners, fabricating the entire pool on-site has significant drawbacks which are not typically found with fiberglass or vinyl liner pool constructions where the manufacturing tolerances can be controlled through off-site manufacturing. Principal among these drawbacks is pool water leakage into the ground, especially proximate to wall fitting positions. Additionally, costs to homeowners and the environment are pollutive costs, as chlorine and other chemicals in pool water migrating into ecosystems, ground water and municipal water can change these fragile environments.
The leakage of pool water into the ground (or in some cases the groundwater entering the pool and mixing with pool water) poses a significant problem for pool owners. Aside from the ever-increasing costs of replenishing the fresh pool water, leakage has other detrimental effects. For instance, over time a significant pool leak may excavate a large volume of earth adjacent to the pool shell and under the apron causing a loss of structural integrity to both the pool wall and the deck. Furthermore, the cost for detecting and repairing pool leaks by professionals are substantial and can cost many times more than the amount of the lost water. Some leaks can be repaired by injecting hydrobaric foams (such as HYPOL (Hydrophilic Polyurethane Prepolyers) a trademark of and available from The Dow Chemical Company of Midland, Mich.) which expand to many times their original volume when exposed to water. This class of polymers has some very important properties for sealing water leaks. First, generally the foams in this class cure rapidly to a slightly ductile texture which bonds, in standing water, to virtually every type of surface (including cement, plaster, PVC and ABS plastics, brass, bronze, stainless steel and chrome). Another important property inherent in hydrobaric foams is that before curing, they react with water and expand. This reaction to water actually causes the foam to migrate, or expand, toward water filled cracks and crevices in a substrate making it a very effective leak treatment. Because of this attribute, the use of hydrobaric foams is typically limited to applications in which the foam can be injected above the water line.
In other situations, the pool must be drained to a level beneath the level of the leak, the plaster surrounding the leaking fitting removed and then the entire fitting re-plastered. The repair of leaking main drains often necessitates emptying the entire volume of the pool for proper repair. This underscores another concern. Some municipalities do not allow pool water to be discharged onto land, waterways and canals or roadways as it may contain high levels of chlorine, bromine and other chemicals. Still others have mandated that pool water cannot be discharged into public sewer systems to protect the aerobic and anaerobic bacterial processes in the treatment plants from algaecides and antiseptics in the pool water. Thus in some municipalities, repairing leaks is even more expensive for the pool owner because of the added expenses for water removal and/or retention.